This paper presents an overview of the attitude determination experiments onboard the University of Minnesota nanosatellite, Minnesat. Minnesat is designed as a test bed for conducting ultra-short baseline GPS attitude determination experiments in Earth orbit. The primary scientific mission of the Minnesat project is to design, develop, and validate an ultra-short baseline GPS attitude determination (AD) system. Minnesat is equipped with a set of sensors to support two independent AD systems that are referred to as the Primary AD System and the GPS AD System. The Primary AD System blends measurements of inertial sensors with measurements of a three-axis magnetometer to estimate Minnesat’s attitude. The GPS AD System blends measurements of inertial sensors with differential carrier phase GPS measurements to estimate Minnesat’s attitude. The Primary AD System is used as a truth source to validate the GPS AD System